The present invention relates to a nitride semiconductor device such as a blue laser used for high-density optical recording.
FIG. 14 illustrates a nitride semiconductor laser device disclosed in Japanese Laid-Open Patent Publication No. 8-153931. This semiconductor laser device includes a sapphire substrate 1 using the (0001) surface as its main surface and a layered structure formed thereon. The layered structure is formed by sequentially growing a first cladding layer 2, an active layer 4, and a second cladding layer 6, which are all made of nitride semiconductor layers using the (0001) surface as their main surfaces. The layered structure is then cut along a surface equivalent to the (1-100) surface of the sapphire substrate 1, to obtain an optical resonator surface. Note that as used herein xe2x80x9cxe2x88x921xe2x80x9d refers to the inversion of xe2x80x9c1xe2x80x9d and xe2x80x9cxe2x88x922xe2x80x9d refers to the inversion of xe2x80x9c2xe2x80x9d.
The conventional nitride semiconductor laser device has a problem as follows. Since the sapphire substrate 1, which is made of hexagonal crystal, uses the (0001) surface as its main surface, there exist only a small number of atomic steps on the surface of the substrate. This tends to cause composition separation in the active layer 4. Occurrence of composition separation in the active layer 4 results in increase in the threshold current of the laser and thus increase in power consumption. It is therefore necessary to minimize occurrence of composition separation in the active layer 4.
The above problem arises not only in a nitride semiconductor laser having an active layer, but also in a nitride semiconductor device having a function region other than the active layer, such as a transistor.
An object of the present invention is to improve the yield of a nitride semiconductor device by minimizing occurrence of composition separation in a function region such as an active region.
In order to attain the above object, the first nitride semiconductor device of the invention includes: a substrate made of a III-V group compound semiconductor containing nitride; and a function region made of a III-V group compound semiconductor layer containing nitride formed on a main surface of the substrate, wherein the main surface of the substrate is a surface tilted from a {0001} surface by an angle in an range of 13xc2x0 to 90xc2x0 inclusive.
According to the first nitride semiconductor device, where the main surface of the substrate is a surface tilted from a {0001} surface by an angle in an range of 13xc2x0 to 90xc2x0 inclusive, occurrence of composition separation in the function region is prevented. This improves the yield of the nitride semiconductor device.
In the first nitride semiconductor device, the main surface of the substrate is preferably perpendicular to a {11-20} surface.
With the above construction, primary cleavage can be performed along the {11-20} surface over the entire substrate by applying a force in the direction along the {11-20} surface with a scribe cutter blade that is positioned perpendicular to the main surface.
In the first nitride semiconductor device, preferably, the function region is an active layer that emits light, and a {11-20} surface of the substrate is an optical resonator surface.
With the above construction, it is possible to realize a semiconductor laser device where the {11-20} surface perpendicular to the main surface of the substrate is the optical resonator surface.
In the first nitride semiconductor device, the main surface of the substrate is preferably a {1-100} surface.
With the above construction, secondary cleavage can be performed along the {0001} surface that is perpendicular to the main surface of the substrate. This facilitates the secondary cleavage and also makes it possible to form a device in the shape of a rectangular parallelepiped.
In the case where the main surface of the substrate is a {1-100} surface, preferably, the function region is an active layer that emits light, and the {0001} surface of the substrate is an optical resonator surface.
With the above construction, it is possible to realize a semiconductor laser device in the shape of a rectangular parallelepiped where the secondary cleavage surface is the optical resonator surface.
In the first nitride semiconductor device, the main surface of the substrate is preferably a surface tilted from the {0001} surface by 28.1xc2x0 in a direction equivalent to a [1-100] direction.
With the above construction, secondary cleavage can be performed along a {1-101} surface that is perpendicular to the main surface of the substrate. This facilitates the secondary cleavage and also makes it possible to form a device in the shape of a rectangular parallelepiped.
In the case where the main surface of the substrate is a surface tilted from the {0001} surface by 28.1xc2x0 in a direction equivalent to a [1-100] direction, preferably, the function region is an active layer that emits light, and a {1-101} surface of the substrate is an optical resonator surface.
With the above construction, it is possible to realize a semiconductor laser device in the shape of a rectangular parallelepiped where the secondary cleavage surface is the optical resonator surface.
The second nitride semiconductor device of the present invention includes a substrate made of a III-V group compound of a III-V group compound semiconductor layer containing nitride semiconductor containing nitride; and a function region made formed on a main surface of the substrate, wherein the main surface of the substrate is perpendicular to a {1-101} surface.
According to the second nitride semiconductor device, the main surface of the substrate has a tilt angle of 13xc2x0 or more from a {0001} surface, and thus occurrence of composition separation in a function region is prevented. This improves the yield of the nitride semiconductor device.
In the second nitride semiconductor device, preferably, the function region is an active layer that emits light, and the {1-101} surface of the substrate is an optical resonator surface.
With the above construction, it is possible to realize a semiconductor laser device where the primary cleavage surface is the optical resonator surface.
In the second nitride semiconductor device, the main surface of the substrate is preferably a {11-20} surface.
With the above construction, secondary cleavage can be performed along a {0001} surface that is perpendicular to the main surface of the substrate. This facilitates the secondary cleavage.
In the case where the main surface of the substrate is a {11-20} surface, preferably, the function region is an active layer that emits light, and a {1-101} surface of the substrate is an optical resonator surface.
With the above construction, it is possible to realize a semiconductor laser device in the shape of a rectangular parallelepiped where the primary cleavage surface is the optical resonator surface.
In the second nitride semiconductor device, the main surface of the substrate is preferably a surface tilted from a {0001} surface by 28.1xc2x0 in a [1-100] direction.
With the above construction, secondary cleavage can be performed along the {11-20} surface that is perpendicular to the main surface of the substrate. This facilitates the secondary cleavage and also makes it possible to form a device in the shape of a rectangular parallelepiped.
In the case where the main surface of the substrate is a surface tilted from a {0001} surface by 28.1xc2x0 in a [1-100] direction, preferably, the function region is an active layer that emits light, and a {11-20} surface of the substrate is an optical resonator surface.
With the above construction, it is possible to realize a semiconductor laser device in the shape of a rectangular parallelepiped where the secondary cleavage surface is the optical resonator surface.
In the case where the main surface of the substrate is a surface tilted from a {0001} surface by 28.1xc2x0 in a [1-100] direction, preferably, the function region is an active layer that emits light, and a {10xe2x80x9410} surface of the substrate is an optical resonator surface.
With the above construction, it is possible to realize a semiconductor laser device where the secondary cleavage surface is the optical resonator surface.
The third nitride semiconductor device of the present invention includes: a substrate made of a III-V group compound semiconductor containing nitride; and a function region made of a III-V group compound semiconductor layer containing nitride formed on a main surface of the substrate, wherein the main surface of the substrate is a surface tilted from a {0001} surface by an angle in an range of 13xc2x0 to 90xc2x0 inclusive.
According to the third nitride semiconductor device, where the main surface of the substrate is a surface tilted from a {0001} surface by an angle in an range of 13xc2x0 to 90xc2x0 inclusive, occurrence of composition separation in a function region is prevented. This improves the yield of the nitride semiconductor device.
In the third nitride semiconductor device, preferably, the function region is an active layer that emits light, and a {1-100} surface of the substrate is an optical resonator surface.
With the above construction, it is possible to realize a semiconductor laser device where the primary cleavage surface is the optical resonator surface.
In the third nitride semiconductor device, the main surface of the substrate is preferably a {11-20} surface.
With the above construction, primary cleavage can be performed along the {11-20} surface over the entire substrate by applying a force in the direction along the {11-20} surface with a scribe cutter blade that is positioned perpendicular to the main surface.
In the case where the main surface of the substrate is a {11-20} surface, preferably, the function region is an active layer that emits light, and the {0001} surface of the substrate is an optical resonator surface.
With the above construction, it is possible to realize a semiconductor laser device in the shape of a rectangular parallelepiped where the secondary cleavage surface is the optical resonator surface.
In the third nitride semiconductor device, the main surface of the substrate is preferably a surface tilted from the {0001} surface by 28.1xc2x0 in a [1-100] direction.
With the above construction, secondary cleavage can be performed along the {1-100} surface that is perpendicular to the main surface of the substrate. This facilitates the secondary cleavage.
In the case where the main surface of the substrate is a surface tilted from the {0001} surface by 28.1xc2x0 in a [1-100] direction, preferably, the function region is an active layer that emits light, and a {10-11} surface of the substrate is an optical resonator surface.
With the above construction, it is possible to realize a semiconductor laser device where the primary cleavage surface is the optical resonator surface.